The present invention relates to the technology of water purification and treatment and particularly pertains to a reverse osmosis membrane element for removing impurities in water such as sands, sludge, colloids, microorganisms, virus, organic materials and inorganic salt and more particularly pertains to a spiral wound reverse osmosis membrane element.
Currently, known reverse osmosis membrane elements are formed by winding purification membrane modules, each of which is formed by laminating a mesh-like treated water guiding member, a reverse osmosis membrane and a mesh-like feed water flow guiding member, around a central treated water tube. The reverse osmosis membrane is folded to form a feed water flow channel therein along its inner surface and the mesh-like feed water flow guiding member is disposed inside the feed water flow channel. A treated water flow channel is formed between outer surfaces of adjacent reverse osmosis membranes after folding and the mesh-like treated water guiding member is disposed inside the treated water flow channel. This kind of spiral wound reverse osmosis membrane element glues the treated water flow channel at two sides at two end surfaces and at one side remote from the central treated water tube by means of glue so that the treated water flow channel has an opening facing towards the central treated water tube; after the water purification member modules are wound around the central treated water tube, the entire outer surface is wrapped by an outer plastic strip and is thereby closed and sealed. In this kind of spiral wound reverse osmosis membrane element, water first enters the feed water flow channel from one end surface of the element; a portion of the water is filtered by the reverse osmosis membranes to form treated water which enters the central treated water tube via the mesh-like treated water guiding members; another portion of the water which has not been filtered forms concentrated water which flows along the mesh-like feed water flow guiding members in the feed water flow channels and is discharged from another end surface of the element. In this kind of spiral wound reverse osmosis membrane element, the direction from which the feed water enters and the direction to which the concentrated water is discharged are the same. However, as the flow channel is wide but the flow path is short, the velocity of the feed water along the flow channel is relatively low, and concentration polarization easily occurs along the membrane surface, therefore resulting in contamination of the membrane element, low desalination rate and treated water volume, as well as poor durability of the membrane element.